Injection-molding machine



Dec. 13, 1949 E. l. VALYl I 2,491,343

INJECTION-MOLDING MACHINE Filed May 6, 1947 4 She'ets-Sheet 1 INVENTOR.[Maw/d. VAL y/ Dec. 13, 1949 Filed May 6, 1947 E. 1. VALYl 2,491,343

INJECTION-MOLDING MACHINE 4 Sheets-Sheet 2 INVENTOR. EMER/K/ VAL. w

BYW/M A T TOR/VEX Dec. 13, 1949 E. l. VALYl 2,491,343

INJECTION-MOLDING MACHINE Filed May 6, 1947 4 Sheets-Sheet 3 A T TORNE YINJECTION-MOLDING MACHINE Filed May 6, 1947 4 Sheets-Sheet 4 IN VEN TOR.

% EME/Q/KZWILY/ BY fm Patented Dec. 13, 1949 UNI'ED STATESINJECTION-IWOLDING MACHINE Application May 6, 1947, Serial No 746,361

9 Claims. (Cl. 18-30) This invention relates to molding machines. Moreparticularly, it relates to a new and improved injection-moldingmachine.

Thermoplastic materials have been molded by a process known as injectionmolding. In such process, the selected thermoplastic material, in aproperly granulated form, was stored in a hopper, the outlet of whichwas connected to a pressure chamber and into which the thermoplasticmaterial dropped by gravity. The outlet of the hopper was controlled bya reciprocating plunger which, in retracted position, permitted themolding material to drop into the pressure chamber. During the moldingoperation, the plunger forced the granulated material from the pressurechamher through a so-called torpedo, which consisted of a number ofholes arranged on a circle. All of the holes entered into a channel atthe nozzle, from where the molding composition reached the mold cavityproper. The torpedo was surrounded by a heating unit, such as a heatedjacket or an electrical band heater, to raise the temperature of themolding composition to that required for injection molding while itpassed the torpedo.

The temperature distribution of the molding composition within thetorpedo was not uniform. Generally, the molding composition could not beraised to a uniform molding temperature throughout its mass, and it wasexceedingly difficult, if not impossible, to provide a consistenttemperature distribution of the molding composition within the torpedofor each of the molding compositions.

An important factor in injection molding is the control of the moistureof the molding composition. Usually, the moisture was driven off beforethe composition was fed into the hopper of the molding machine. However,frequently the molding composition became moist while stored in thehopper. To avoid this, extremely inconvenient means were resorted to inorder to insure dryness of the molding composition.

As previously mentioned, the above-described molding machine requiredthe molding composition to be in properly granulated form and therebyimposed a certain restriction on the type of plastic used. Thus, forexample, if the plastic should become tacky soft, as might happen on ahot summer day, the feed, abov described, would not function at all.Hence, it was almost impossible to mold substances such as commercialwax.

In certain instances, it is technically desirable to mold molding wax,low molecular weight resins, nylon, and polyethylene in a condition ofextremely low viscosity or even in. a liquid condition. Such practice,wherein th requirementsv as to temperature control are increasinglyimportant because the molding temperature is critical within a fewdegrees (F), could not be carried out by the aforementioned apparatus.

In carrying out the molding cycle of the previously described process,the pressure plunger first had to force a considerable amount of coldelastic granulated mold composition into the torpedo and through thismedium extrude from the torpedo the molding composition that had beenreviously brought to the temperature thereof. Since the temperaturedistribution of the mold-; ing composition was inadequate, highpressures, such as 16900430300 pounds per square inch, had to be used toinsure flow of those portions of the molding composition that had notreached a sufficient degree of plasticity.

An object of this invention is to provide a new and improved moldingmachine, particularly a new and improved injection-molding machine.

Another object of this invention is to provide a molding machine whereinthe temperature dis tribution is substantially uniform throughout themolding composition.

An additional object of this invention is to provide a molding machinewherein the molding composition will be protected from moisture andoxygen.

A further object of this invention is to provide a molding machinewherein the consistency of the molding composition at moldingtemperature will not influence the operation of the machine in any way.

A still further object of this invention is to provide a molding machinewherein molding can be accomplished at pressures considerably lower thanthat required by the conventional method of injection molding.

A still further object of this invention is to provide an injectioncylinder and a storage cylinder and means to transfer the contents ofthe storage cylinder to the injection cylinder when the contents of theinjection cylinder reaches a predetermined level.

Other and additional objects will become apparent hereinafter.

The objects of the invention are accomplished, in general, by providingan injection-molding machine, having a reciprocable platen carrying thedie members together with a core plate and an ejector plate, with aninjection cylinder and a storage cylinder within a heated jacket soarranged that the heating medium in said jacket will completely anduniformly heat the contents of both cylinders. The injection cylinder isprovided at the bottom thereof with a passage having at its outer end anozzle which is adapted to communicate with a gate leading to the moldcavities in the die members whereby, upon the application of. pressure,as by a plunger, to the contents in the injection cylinder, themoldingcomposition will be extruded therefrom into the mold cavities. Avalve, which at predetermined! intervals opens and closes the passageleading. from the pressure cylinder to the nozzle, controls theextrusion of the molding composition from the pressure cylinder.transfer the contents of the storage cylinder to the injection cylinderwhen the: contents in the latter has reached a predetermined level.

In one embodiment of the invention, the" injection cylinder and thestorage cylinder are connected. by a valve-controlled passage, whichvalve: is: actuated at a predetermined interval. to permit the transfer.The transfer of the contents of the storage cylinder is: effected bymeans of a storage cylinder plunger which is actuated at the requiredtime. During. this operation, the pressure on the injection cylinderplunger is released. Normally, the storage cyli'nder plunger rests onthe contents of the storage cylinder whereby such contents is protectedfrom moisture and oxygen.

In operation, both cylinders are filled with. the molding compositionand both plungers are lowcred into the cylinders so that they will reston the contents thereof. After the composition has been brought to thedesired temperature, the movable platen is elevated into moldingposition, and pressure on the contents of the injection cylinder isapplied through the injection cylinder plunger. At this time, thestorage cylinder plunger rests on the contents in the storagecylinderwithout exerting any substantial pressure. The valve controlling thefeed from the injection cylinder is operated to permit the moldingcomposition to be extruded into the die cavity through the nozzle. Fromnowon, the plunger in the injection cylinder will maintain the moldingcomposition therein under constant pressure. and will not reciprocatewhile the plunger in the storage cylinder merely rests on thecomposition therein without exerting any pressure. The opening andclosing of the valve will control extrusion into the injection mold.After each, injection and solidification of the molding, the movableplaten is retracted, the molding removed, and the platen returned tomolding position. Operation in this manner is continued until thecontents of the injection cylinder has reached a predetermined level,whereupon the valve controlling communication between the. injectioncylinder and the storage cylinder will be opened automatically, whilethe valve controlling extrusion from the injection cylinder will beclosed. At this time, pressure is applied to the contents in the storagecylinder by the plunger therein and pressure on the injection cylinderplunger released so that, as the injection cylinder is being filled, theplunger therein will rise. After the transfer has been completed,operation is resumed.

While the molding operation is in progress, the storage cylinder isrefilled and the storage cylinder plunger disposed in the storagecylinder so that it will rest on the contents therein. Usually, the twocylinders are made of a size so Means are provided to that there will besufiicient material for a full days operation. In such case, thepreferred mode of operation is to load both cylinders at the end of theday and allow the molding composition to reach the proper moldingtemperature throughout its mass by the beginning of the next day.

The elevation and retraction of the movable platen and the operation ofthe various plungers as well as the operation of the various valves areperformed in the desired timed sequence. In the preferred embodiment ofthe invention, the operations are secured by pneumatic-actuatedmeanswhich. are. operated in timed sequence by electrical mechanisms.

The invention will be more clearly understood by reference to thefollowing detailed description when taken in connection with theaccompanying drawings, wherein:

Figure 1 is an elevation of an injection-molding machine embodying thepresent invention;

Figure 2 is a side View of. themachine shown in Figure 1;

Figure 3 is a partial vertical section showing the injection and storagecylinders, the plungers cooperating therewith, the transfer valve, andthe valve controlling the extrusion from the in.- jection cylinder;

Figure 4 is a top plan view showing the arrangement of the pressure andstorage, cylinders within the jacket;

Figure 5 is asection taken on the line 55 of Figure 4; and

Figure 6 is a schematic diagram showing the hydraulic and electriccircuits.

Referring now to the drawings, wherein like reference numerals designatelike parts, the reference numeral ill designates a plurality of verticalposts, the lower ends of which are threadedly secured in an approriatebase l2 and maintained in secured position by the nuts [4. At the top,the posts ill carry a plate it, and the rods are secured thereto bymeans of nuts l 8 and 26. It is to be understood that the portions ofthe posts which cooperate with the nuts l4, l8

and 2:; are threaded.

A platen 22, slidably mounted on the posts It, is secured to one end ofa piston rod 24, the other end of which carries a reciprocable piston.

' 25' slidably disposed in a hydraulic cylinder 28 appropriately mountedin the machine beneath the platen. A housing 3!], appropriately securedon the posts Ill and base !2, encloses the cylinder 28.

The movable platen 22 is of the usual type wherein the molding cavity isformed by a pair of complemental, relatively movable die members and canbe provided with a core plate and. ejector plate carrying; ejector pins.Preferably, the movable platen is of a construction wherein the coreplate and the ejector plate are removed by pneumatic-actuated means,such as shown in copending applications Serial No. 699,547, filedSeptember 26, 1946, now Patent No. 2,485,336 and Serial Nos. 725,381 and725,382, filed January 30, 1947 now Patent Nos. 2,485,283 and 2,485,284.Since the details of construction of the movable platen and theassociated stripper mechanism form no part of this invention, furtherdescription thereof is deemed unnecessary.

A plate 32 is rigidly secured on the posts it) in any convenient mannerand, as will hereafter appear, it constitutes a fixed injector plate. An

injection cylinder 34 and a storage cylinder 36 are secured on the plate32 in spaced relationship, as shown in Figures 3, 4 and 5. The injectioncylinder 34 cooperates with a passage 36 which communicates with anextrusion nozzle 40 whereby the contents of the injection cylinder canbe extruded into the molding cavity of the movable platen 22, as willhereafter become apparent.

Both the injection cylinder 34 and the storage cylinder 36 are providedadjacent the bottoms thereof with Openings 42 and 4d respectively, andcommunication therebctween is controlled by a valve 46 mounted in ahousing 48 located between and secured, as by welding, to bothcylinders. The housing 48 is also secured on the plate 32. It is to benoted that the plate 32 is provided with a hole to accommodate the valve46. The valve 46 is carried at one end of a valve stem 56, the other endof the valve stem 56 being secured to one end of a piston rod 52. Theother end of the piston rod 52 is secured to a reciprocable piston 54slidably mounted in a hy draulic cylinder 56 appropriately mounted inthe machine. It is apparent that upon the raising and lowering of thevalve 46 through the actua tion of the piston 5 in the necessarydirection, communication between the injection cylinder 34 and thestorage cylinder 36 through the openings 42 and 44 may be made orinterrupted.

The extrusion of the molding composition from the injection cylinder 34through the passage 38 and the nozzle 48 is controlled by a valve.Though any type of valve can be used, in the form shown a slide valve 66is slidably mounted in a valve casing 52 secured to the under surface ofthe plate 32. The valve 66 is carried at one end of a stem 63, the otherend of which is secured to one end of a piston rod 64. The other end ofthe piston rod 64 carries a reciprocable piston 66 slidably mounted in ahydraulic cylinder 68 appropriately mounted in the machine. It ismanifest that upon reciprocation of the piston 66, the valve 68 willopen and close the discharge from the injection cylinder 34.

In order to extrude the contents from the injection cylinder through thenozzle 46, there is provided a plunger 16 carried at one end of a pistonrod 12. The other end of the piston rod 12 is secured to a reciprocablepiston 14 slidably mounted in a hydraulic cylinder 16 appropriatelymounted in the machine.

A plunger 86 cooperates with the storage cylinder 36 and it is securedto one end of a piston rod 82. On its opposite end, the piston rod 82 isprovided with a reciprocabie piston 84 which is slidably mounted in ahydraulic cylinder 66 appropriately mounted in the machine.

Both cylinders E i and 36 are disposed within a jacket 66 which servesas a reservoir for a heating medium, such as oil, which can becirculated or stationary. Suitable known means (not shown) are providedfor heatin the oil to and maintaining it at the desired temperature. Thewalls of the jacket 98 are welded, as shown in Figure 4, to cylindricalsupports 62 secured to the plate 32. Appropriate reinforcing elements 94and 96 respectively secure the injection cylinder 34 to the adjacentmembers 62 and the walls of the jacket 96. In general, the jacket 56 isof a height lower than that of the cylinders 34 and 36.

As previously mentioned, the hydraulic mecha nisms are operated in timedsequence in accordance with the desired operation by electricalactuating means. The hydraulic and electrical circuits shownschematically in Figure 6 will now be described.

Referring to Figure 6, hydraulic pressure i supplied by a pump I58 to ahigh pressure line I5I which is connected by a line I52 to asolenoidoperated four-way valve I53, by a line I54 to amanually-operated two-way valve I55, by a line I56 to asolenoid-operated two-way valve I51, and by a line I58 to asolenoid-operated four-way valve 558. High pressure fluid is alsosupplied by the pump 158 through a line I68 to a solenoidoperatedfour-Way valve i6I. Low pressure fluid is returned to the pump I58 by areturn line I65. This line is connected by a line I66 to the valve MI,by a line I61 to the valve I53, by a line I68 to the valve I55, by aline I69 to the valve I51, and by a line I16 to the valve I59.

The valve i6I is connected by lines I15 and I16 to the bottom and toprespectively of the cylinder 28. This valve i6I is of thedoublesolenoid-actuated type having solenoids I11 and I18 which areadapted respectively, when energized, to connect the high pressure lineM6 to the line I15 and the low pressure line I66 to the line I16, orvice versa, for raising or lowering the piston 25.

The valve I53 is connected by lines I85? and I8l to the opposite ends ofthe cylinder 68 and is provided with a solenoid I83 which is adapted,when energized, to connect the line 86 to the high pressure line I52 andthe line I8! to the low pressure line I61 so that when the solenoid I 83is energized the piston 66 is moved to the right, and when the solenoidI83 is de-energized the reverse connections are made to shift the piston66 to the left.

The manual valve I is connected by a line I to the lower end of thecylinder 16 and is adapted to connect the high pressure line I54 or thelow pressure line I68 to the line I85 according to the position of thevalve I55.

The valve I51 is connected by a line I8ii to the top of the cylinder 16and is actuated by a solenoid I81 in a manner to connect the highpressure line I52 to the line I86 when the solenoid i81 is energized andto connect the low pressure line I69 to the line I66 when the solenoidI81 is de-energized.

The four-way solenoid-actuated valve I59 is connected by lines I96 andI9I to the bottom and top respectively of the cylinder 86 and to thebottom and top respectively of the cylinder 56. A delayed actionsequence valve I92 is interposed in the connection from the line I96 tothe bottom of the cylinder 86, and a delayed action sequence valve I63is interposed in the connection from the line Hi to the top of thecylinder 56. The valve I59 is actuated by a solenoid I94 and. is soconstructed that when the solenoid I94 is energized, the high pressureline I53 is connected to the line I9I and the low pressure line E16 isconnected to the line I93, and, when de-energized, the reverseconnection takes place to con meet the low pressure line I18 to the lineI9I andthe high pressure line I58 to the line I98.

The solenoid I11 is connected by a lead 295 to one side of a powersupply line (not shown) and by a lead 2! I through a pair of manualswitches 2 I2 in series and switch 2 I3 to a lead 2 M which is connectedto the other side of the power supply line. The switch 253 is alsoconnected by a lead 2E5 to a lead 2 I6 which is connected to one contactof a switch 2I1, thence from the other contact of the switch 2I1 by alead 2I8 to a switch 2I9 and by a lead 228 to a contact 22I of a relay222. Contact 223 of. the relay 222 is connected by a lead 224' to oneside of the solenoid ltl, the other side of which is connected by a lead225 to the return. side of the power supply. The lead 2l5 is alsoconnected by a lead 232' to contacts 231' and 232 of a switch 283.Contact 23 of the switch 233 is connected by a lead 235 to a contact 235of a switch 23?. Contact 238 of the switch 23l is connected' by a lead239 to contact an of a switch 221. Contact 242 of the switch 2%! isconnected by a lead to the lead 2H. The contact 235 of the switch 23l isalso connectedto a contact 225 of said switch. The contact 22b of theswitch 25'? is connected by a lead 2 to one side of the solenoid I28,the other side or which is connected by a lead 2% to the return side ofthe power supply line. Contact of. the switch 233 is connected by a leadZill to the lead 2.

The lead 23!? is also connected by a lead 252 to a contact 253 of aswitch 25 i, thence by a lead 255 to a contact 25% of a switch 25?having a second contact 258 which is connected by a lead 25?; tocontacts 266 and of the relay 222. Contact 251 of the relay 222 isconnected a lead 222 to one side of the solenoid led, the other side orwhich is connected by a lead to the return side of the power supplyline. A contact 265 of the switch 252 is connected by a lead to one sideof the coil 26? of the relay 222, the other side of which is connectedby a lead 252 to the return side of the power supply line. The coil 25'!is also connected to a contact 2 12 of the relay 222, which completes aholding circuit.

The switches 2i? and 245 are normally held open when the platen 22 is inits lower position by a bar 2T5 attached to the platen 22, havingsurfaces 2% and 2?? adapted to engage and hold the switches 2| l and 2&5respectively in open position. The bar 215 releases and closes theswitches when the platen has been elevated from its lower position. Theswitch 232 is actuated by a bell lever 2l3 having an arm 239 which isengaged by a finger 28E attached to the bar 2"5 to close the contacts235 and 238 when the bar 2'55 and platen 22 reach their lower positions.The Valve 22 carries a plunger 22l which is adapted to engage an arm 282of the bell lever 2l2 for actuating the same to close the contacts 255and when the valve 82 and plunger 23! reach their right-hand positions.

The piston rod 6 5 carries an arm which, when the rod is in itsleft-hand position, actuates the switch 233 to hold the contacts 23E and224 closed. When the piston rod 64 and the arm 2'85 move to the right,the switch 233 is released and is spring-actuated to close the contacts222 and 250.

The piston rod 72 carries an arm 28% which engages the switch 25? whenthe rod is in its position to open the contacts 256 and The arm 288 isadapted to engage the switch 25c vixen in its lower position to closethe contacts and 265.

One side of the solenoid E83 is connected by lead 29:3 to one side ofthe power supply lin The other side of the solenoid M3 is connected by alead 29! to a timer 222 which is adapted, when energized, to maintain aclosed circuit for a predetermined period of time and then to break thecircuit. The timer 222 is connected by a lead 293 to a contact 252 of aswitch 295, a second con tact 29%; of which is connected by lead to aswitch 298 and thence by a lead 2% to the other side of a power supplyline. The switch 225 is of 8 the pressure-actuated type and is connectedby a duct Edd-to the line 1'55 to receive pressure therefrom and isadapted to close the contacts 292 and 2% in response to a predeterminedpressure in the line H5.

In the operation of this system, the switches 2E3, 222 and M9 are firstclosed. The operating cycle is then initiated by the operator manuallyclosing the two manual switches 2 i2. When these switches are closed, acircuit is completed from the lead 2!!) through the lead 2H to thesolenoid l'll, thereby energizing the solenoid ill and actuating thevalve liii in a direction to supply high pressure fluid to the bottom ofthe cylinder 28. This causes the piston 26 and the platen 22 to rise andto bring the die into position to receive a charge from the injectioncylinder 34.

When the platen 22 rises, the switch 2!? is closed, thereby completing acircuit from the lead 2h; through leads 2i5 and 2|2, switch 2H, lead252, switch 2l2, lead 226, closed contacts 22E and 223 of the relay 222,and lead 226 to the solenoid 58?. Actuation of the solenoid l8? shiftsthe valve 53 in a direction to supply fluid under high pressure throughthe line 586 to the top of the cylinder 15, thereby forcing the piston ii and the plunger l8 downwardl to apply pressure to the molding materialin the injection cylinder Raising of the platen 22 also closes theswitch 24 I, establishing a holding circuit for the'solenoid ill fromlead 2 Hi through leads 2l5, 232, contacts 23! and 222 of switch 233,lead contacts 225 and 238 of switch 237, lead 239, contacts 2% and 222of switch Edi, and lead 243 back to the lead 2H. The solenoid ill thusremains energized after the operator releases the manual switches 2l2.

After the platen 22 reaches its upper position, pressure is built up inthe lower end of the cylinder 2c and the line 5'55 to a value such thatthe pressure-actuated switch 295 closes. When this switch closes, acircuit is established from the lead 292 through switch 298, lead iS'l,contacts 296 and 2%, lead 293, timer 292, lead 29! to one side of thesolenoid I83, thence by the lead 290 to the other side of the powersupply line. Energization of the solenoid l83 actuates the valve 153 toapply fluid under high pressure to the head end of the cylinder 63,thereby forcing the piston 56 to the right and opening the valve 653 topermit the molding material to be injected from the cylinder 32 into themold on the platen 22. When the piston rod 62 moves to the right, thecontacts 23! and 23d of the switch 233 are opened and the contacts 232and 252 are closed. Closing the contacts 222 and 258 establishes theholding circuit for the solenoid Ill through the lead 25L therebycutting the switch 23? out of the holding circuit. When the piston 66and the plunger 64 reach their extreme right-hand positions, the switch22l is actuated to open the contact 23B and close the contact 2%,thereby setting up a circuit to the solenoid H8. The circuit, however,is not completed until the contacts 23! and 23-; are again closed at theend of the return stroke of the piston 66.

At the end of the period for which the timer 222 is set, the timer 222breaks the circuit to the solenoid H33, thereby de-energizing the same,and actuating the valve 553 to supply fluid under high pressure throughthe line Elli to the right-hand side of the cylinder 58. The piston 56thereupon returns to its original position, closing the valve 52 and atthe end of its return stroke closing the contacts 23! and 234. Whenthese contacts are closed, the solenoid H8 is actuated to reverse theposition of the valve llil and supply fluid under high pressure to thetop of the cylinder 28 for retracting the piston 28 and the platen 22.When the platen 22 reaches the lower end of its stroke, the switch 23'!is again actuated to close the contacts 25% and 238 and the switches 24!and 2 ill are opened, thereby resetting the system in its originalposition. Release of the pressure in the duct I15 by actuation of thevalve IEI causes the pressure-actuated switch 295 to open. The moldingcycle is now completed and the molded articles may be ejected in theusual manner. The system is then ready for a second cycle of operationwhen the manual switches 212 are again closed.

As a result of repeated injection-molding operations, the moldingmaterial in the injection cylinder 34 becomes depleted and the plungerit falls to successively lower positions. When the plunger i falls to aposition such that the switch 254 is closed, a circuit is establishedfrom the lead 235 through the lead .252, contacts 253 and 265, and lead255 to coil 2%? of the relay 222, thereby actuating the relay andbreaking the contacts 223 and 225 and closing contacts ace and 26!.Break ng of the contacts 22! and 223 de-energizes the solenoid l3! andactuates the valve 5! to relieve the pressure at the top of the cylinder16. Closing of the contacts 250 and 26H sets up a circuit from the lead252, 255, switch 251, lead 259 through contacts 250 and 2E! and lead 252to the solenoid ls l, thereby actuating the valve 559 to supply fluidunder high pressure through the line let to the top of the cylinder 86and through the delay action sequence valve E93 to the top of thecylinder '55. The pressure in the top of the cylinder 86 causes thepiston M to be depressed, thereby forcing the plunger 80 into thestorage cylinder 35 and building up pressure -1- on the molding materialtherein. The delay action of the valve its is designed to allow thepressure to be built up in the storage cylinder 35 before the valve 56opens. Thereafter, the pressure is supplied to the top of the cylinder5% to open the valve it. The pressure of the plunger 8h thereupon forcesthe molding material from the storage cylinder 36 through the valve 46into the injection cylinder 34, recharging the cylinder es and causingthe plunger 10 to rise. This continues until the plunger it reaches aposition to open the switch 25'l. When this occurs, the circuit to thesolenoid 53 i is broken and the Valve its is shifted to supply highpressure fluid tluough the line see to the lower part of the cylinderfor elevating the piston 54 and closing the valve The fluid pressure isthen supplied through the delay action valve I92 to the lower part ofthe cylinder 85 for elevating the piston 84 and the plunger 8d torelieve pressure on the reservoir 35. During the period while the switch254 is open, a holding circuit for the coil 26'! is established throughthe contacts 269 and 210.

The system thus operates automatically to replenish the charge in theinjection cylinder 34 as required. The cylinder 34 may be rechargedmanually when the supply of reserve material becomes low. The manualvalve I55 permits pressure to be supplied through the line 985 to thebottom of the cylinder 56 when it is desired to relieve the pressure onthe molding material in the cylinder 34 for recharging.

Though specific valves have been described for controlling the extrusionand the transfer respectively, it is to be understood that the inven- 10tion is not restricted thereto and that any other types of valves can beused.

This invention provides an injection-molding machine wherein, due to thelarge bulk of molding material contained within the single heating unitand due to the long time during which the molding composition is held atthe required temperature, temperature distribution within the mold canbe controlled with extreme accuracy and uniform distribution within lessthan 5 F. can be accomplished. After the composition in the twocylinders has reached a uniform temperature, such uniform temperaturecan be maintained at all times while the machine is in op-. eration.After the dry molding composition has been fed into the two cylinders,no moisture will have access to the molding compositions since thecylinders are sufficiently sealed by their respective plungers. Thisseal also prevents oxygen from reaching the heated molding composition,thus protecting it from excessive heat degradation.

Due to the details of construction of the machine, the consistency ofthe molding composition at molding temperatures will not influence theoperation. of the machine in any way. The molding composition may besticky or in any stage of low viscosity. Since pressure is maintained onthe molding at all times, and due to the uniformity of temperaturewithin the molding composition, molding can be accomplished at pressuresbetween and 2,000 pounds per square inch, whereas pressures of from10,000 to 30.000 pounds per square inch are required by conventionalmethods of molding.

Since it is obvious that many changes and modifications can be made inthe above-described details without departing from the nature and spiritof the invention, it is to be understood that the invention is not to belimited to the details described herein except as set forth in theappended claims.

I claim:

I. In an injection-molding machine, an injection cylinder for containingthe molding composition, a storage cylinder for containing a reserve ofthe molding composition, means providing communication between saidcylinders, a valve controlling said communication, means including aplunger adapted to apply pressure on the contents of said injectioncylinder to extrude the composition from said injection cylinder, aplunger normally sealing the contents in the storage cylinder, means toactuate the injection cylinder plunger to apply pressure on the contentsin said injection cylinder, and means actuated by the injection cylinderplunger to apply pressure on the storage cylinder plunger when theinjection cylinder plunger reaches a predetermined level, to release thepressure on the injection cylinder plunger, and to actuate the valve topermit communication between said cylinders after the storage cylinderplunger is actuated.

2. In an injection-molding machine, an injection cylinder for containingthe molding composition, a storage cylinder for containing a reserve ofthe molding composition, means providing communication between saidcylinders, a valve controlling said communication, a nozzle cooperatingwith the bottom of said injection cylinder and through which the moldingcomposition is extruded, a plunger adapted to apply pressure on thecontents of said injection cylinder, die members in which the extrudedcomposition is injected, a platen carrying said die members, meansassume to movesaid platen at predetermined intervals to dispose said diemembers in and out of molding position, a, valve controlling theextrusion from said injection cylindcrthrough said nozzle, meansactuated by said aplaten to actuate said valve, a plunger normallysealing the contents in the storage cylindenmeans to actuate theinjection cylin der plunger to apply pressure on the contents in saidinjection cylinder, and means actuated by said injection cylinderplunger to apply pressure on the storage cylinder plunger at apredetermined time, to release the pressure on the injection cylinderplunger, and to actuate the valve to provide communication between saidcylinders after the storage cylinder plunger is actuated.

3. In an injectiommolding machine, an injection cylinder for containingthe molding composition, a storage cylinder for containing a reserve or"the molding composition, means providing communication between saidcylinders, a valve control-ling said communication, a jacket surroundingsaid cylinders and valve to provide a reservoir for a heating medium,means including a plunger adapted to apply pressure-on the contents ofsaid injection cylinder to extrude the composition from said injectioncylinderg aplunger normally sealing the contents in the storagecylinder, means to actuate the injection cylinder plunger to applypressure on the contents in said injection cylinder, and means actuatedby the injection cylinder plunger to apply pressure on the storagecylinder plunger when the injection cylinder plunger reaches apredetermined level, to release the pressure on the injection cylinderplunger, and to actuate the valve to permit communication between saidcylinders after the strage cylinder plunger is actuated.

4.. In an injection-molding machine, an injectioncyli-nder forcontaining the molding composition, a storage cylinder for containing areserve ofthe molding composition, means providing communication betweensaid cylinders, a valve controlling said communication, a jacketsurrounding said -cylinders and valve to provide a reservoir for aheating medium, a nozzle cooperating with the bottom of said injectioncylinder and through which the molding composition is extruded, aplunger adapted to apply pressure on the contents of said injectioncylinder, die members in which the extruded composition is injected, aplaten carrying said die members, means to move said platen atpredetermined intervals to dispose said die members in and out ofmolding position, a valve controlling the extrusion from said injectioncylinder through said nozzle, means actuated by said platen to actuatesaid valve, a plunger normally-sealingthe contents in the stor agecylinder, means actuated by said platen to actuate the injectioncylinder plunger to apply pressure on the contents in said injectioncylinder, and means actuated by the injection cylinder plunger to applypressureon the storage cylinder plunger at a predet rmined time, torelease the pressure on the injection cylinder plunger, and to actuatethe valve to provide communication between said cylinders after thestorage cylinder plunger is actuated.

5. An injection-molding apparatus comprising an injectioncylinder-containingmolding material, a plunger to apply pressure to saidmaterial, a discharge passageoommunicating with said cylinder, a valvenormally closing said passage, a platen carrying a die mounted to beadvanced to molding position and to be retracted therefrom, means. toadvance said platen to molding position, pressure means actuated by theadvance of said platen to actuate said plunger to apply molding pressureto said molding material, means actuated in response to the elevation ofsaid platen for opening said valve for a predetermined period of timefor the injection of the molding material, means responsive to theclosing of said valve 'for retracting said platen, and means actuated bythe retraction of said platen to relieve the pressure on the plunger.

6. An injection-molding apparatus comprising an injection cylindercontaining molding material, a plunger to apply pressure to saidmaterial, a reservoir containing additionalmaterial', a plunger to applypressure to the material in said reservoir, a valve interconnecting saidcylinder with said reservoir, means-responsive to the lowerin of thecylinder plunger to a predetermined position to apply pressure to saidreservoir plunger for exerting pressure on the material in saidreservoir, timed means to open said valve after the material in saidreservoir has been brought under pressure whereby material is suppliedto said reservoir to replenish said cylinder, and means responsive tothe elevation of said cylinder plunger to a predetermined position tofirst close said valve and then relieve the pressure on said reservoirplunger.

'7. In an injection-molding apparatus, an injection cylinder containinginjection-molding material, a plunger in said injection cylinder toapply pressure to said material, a discharge passage communicating withsaid injection cylinder, a valve to close said passage, a platencarrying a mold and movable to andfrom molding position in registrationwith said discharge passage, pistons connected to actuate said platen,said. plunger andsaid valve, hydraulic cylinders associated with saidpistons, a source of fluid pressure, means including hydraulic valvesconnecting said source to each of said hydraulic cylinders forcontrolling the actuation of said pistons, means including an electriccircuit connected to actuate the platen control valve to cause theplaten piston to elevate the platen into molding position, anelectricswitch actuated by elevation of said platen, an electricalcircuit including said switch and connected to actuate the plungercontrol valve for causing said plunger to apply pressure to the moldingmaterial in said injection cylinder, an electric circuit connected toactuate the valve control cylinder to opensaid valve for molding, apressure-actuated switch in said ,lasticircuit responsive to hydraulicpressure built up. in said platen piston cylinder to closesaidlastcircuit, timed means for de-energizing said last circuit after a.predetermined molding period for again closing said valve, andelectrically controlled means responsive to the closing of said valvefor reversing the position of the platen control valve to retract saidplaten.

8. An injection-molding system comprising an injection cylindercontaining molding material, a first plunger to apply pressure to saidmaterial, a first hydraulicallyactuated piston to actuate said plungenadischarge passage communicating with said cylinder, a first Valvenormally closing said passage, a second hydraulically actuatedpistonconnected to control said valve, a platen to carry a mold andmounted to advance to molding position and to be retracted therefrom, athird hydraulically actuated. pistonv connected to actuate said platen,a source of fluid pressure connected to actuatethe respective pistons, afirst solenoidcontrolled valve connected to control the supply of saidfluid pressure to said third piston for elevating and retracting saidplaten, a second solenoid-actuated valve connected to control the supplyof fluid pressure to said second piston for closing or opening saidvalve, a third solenoid-controlled valve connected to control the fluidpressure to said first piston for applying pressure to or relieving thepressure on said first plunger, an energizing circuit for said firstsolenoidcontrolled valve including a manual switch for initiating theoperation thereof to elevate said platen, a second electric circuitcontrolling said third solenoidcontrolled valve, a second switch meansactuated in response to the elevation of said platen to energize saidsecond circuit for causing said first plunger to exert pressure on themolding material, a third electric circuit, connected to actuate saidsecond solenoid-controlled valve including a switch responsive to theelevation of said platen and connected to energize said third circuit toopen said first valve and a timer connected to deenergize said thirdcircuit after a predetermined period of time to close said first valve,a fourth electric circuit connected to control said firstsolenoid-controlled valve for reversing the fluid pressure on said thirdpiston and retracting said platen, a switch responsive to the closing ofsaid first valve to actuate said fourth circuit for retracting saidplaten, and means responsive to the retraction of said platen to opensaid second switch means for thereby relieving the pressure on saidplunger, a reservoir for molding material, a passage connecting saidreservoir with said cylinder, a second valve normally closing saidpassage, fluid-actuated pistons connected to apply pressure to thematerial in said reservoir and to actuate said second valve, a fourthsolenoid-actuated valve connected to control the fluid pressure suppliedto said reservoir, a relay connected to control the energization of saidfourth solenoidactuated valve, a third switch means responsive to thelowering of said plunger to actuate said relay, a fourth switch meansactuated by said relay for actuating said fourth solenoid-actuated valveto apply pressure to said material in said reservoir and to open saidsecond valve for replenishing said cylinder from said reservoir, andmeans responsive to the elevation of said plunger for releasing saidrelay for closing said second valve and for relieving the pressure onsaid reservoir, and delay action valves in said fluid pressure line tocause said second valve to open after pressure has been applied to saidreservoir and to close before the pressure in said reservoir has beenrelieved.

9. In an injection-molding machine, an injection cylinder for containingthe molding composition, a storage cylinder for containing a reserve ofthe molding composition, means providing communication between saidcylinders, a valve controlling said communication, means including aplunger adapted to apply pressure on the contents of said injectioncylinder to extrude the composition from said injection cylinder, meansto actuate the injection cylinder plunger to apply pressure on thecontents in said injection cylinder, pressure means applying pressure tosaid storage cylinder, and means actuated by the injection plunger whenthe injection cylinder plunger reaches a predetermined level to actuatesaid pressure means so as to apply pressure on the storage cylinder, torelease the pressure on the injection cylinder plunger, and to actuatesaid valve to permit communication between said cylinders after thestorage cylinder pressure means is actuated.

EMERIK I. VALYI.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,993,942 Novotny Mar. 12, 19352,043,584 Husted June 9, 1936 2,107,190 Shaw Feb. 1, 1938 2,187,212MacMillin Jan. 16, 1940 2,202,140 Burroughs May 28, 1940 2,359,840Goessling Oct. 10, 1944

